Vibratory drill apparatus

ABSTRACT

The subject matter of this invention is a rock drill apparatus whose kinematics is based on the resonance of two massive members connected through a member possessing the characteristics of a stiff spring. This resonant system is driven to a high rate of vibratory motion through an hydromechanical actuator, because of which the attached bit strikes repeated blows on the rock formation and thus effects drilling.

United States Patent Nick D. Diamantides Cuyahoga Falls;

William L. Rinks, Bath, both of Ohio 841,177

June 2, 1969 Oct. 5, 1971 Inventors Appl. No. Filed Patented VIBRATORY DRILL APPARATUS 24 Claims, 7 Drawing Figs.

U.S.Cl 175/56 Int. Cl E2lb 5/00, B06b1/18,B06b1/14 Field ofSearch 175/55,56; 173/49; 137/815 References Cited UNITED STATES PATENTS 12/1937 Johansen 3/1954 Bodine,Jr. 9/1960 Bodine et aL... 2/1961 Bodine, Jr.

Primary Examiner-James A. Leppink ABSTRACT: The subject matter of this invention is a rock drill apparatus whose kinematics is based on the resonance of two massive members connected through a member possessing the characteristics of a stiff spring. This resonant system is driven to a high rate of vibratory motion through an hydromechanical actuator, because of which the attached bit strikes repeated blows on the rock formation and thus effects drilling.

VIBRATORY DRILL APPARATUS This invention relates to the field of rock penetrating tools, and in particular to an improvement of a rock drill.

in applicants Pat. application, Ser. No. 734,048 filed on June 3, 1968, and found allowable per examiner's communication mailed on Feb. 18, 1969, there was disclosed a vibratory drill apparatus driven by fluid means and capable of penetrating rock formations from the softest to the hardest type, said apparatus being safe in operation, simple in construction and efficient from the viewpoints of energy consumption, penetration rate, handling and repairing simplicity.

More specifically, the above referred to application disclosed the concept of employing a vibratory drill assembly to be used in conjunction with conventional oil well rotary drilling apparatus, including a vibrator mass and a head mass to which the rock crushing bit is attached on the bottom, these two masses being coupled together along their common longitudinal or vertical axis by at least one hearing or connecting member having stiff axial spring characteristics, whereby limited axial displacement of one mass with respect to the other would result upon the application of axial force between said two masses. This system of two vibrating masses is resiliently attached in the axial direction to an adapter above them and affixed at the bottom of the drill stem or string, through a second bearing or coupling member having soft axial spring characteristics and connecting the stem adapter to one of the two vibrating masses.

The vibrator and head masses are forced into vibratory motions of opposing directions by a power oscillator acting upon an inlet flow of pressurized fluid conventionally supplied through the drill string and stem adapter and converting the continuous inlet flow into a cyclic flow. This cyclic flow in turn is fed into one or more piston chambers formed between the vibrator and the head and causes said opposing vibratory motion of the vibrator and head masses. The aforesaid power oscillator may be or either a purely fluidic type with no moving solid parts or of a resiliently held and mechanical nature as described in great detail in the aforesaid application.

While the above system of vibratory drill apparatus fulfills the basic requirements of effectiveness, simplicity, and long life under operational conditions, it has become obvious to the applicants that further improvements beyond the specific implementation first disclosed can be had and increase of its utility achieved. In this revised implementation, the aforesaid connecting member, coupling the vibrator and head masses and having stiff axial spring characteristics, is constructed in the form of a long metal sleeve capable of withstanding severe FIG. 6 is a cross-sectional view of the drill comprising the sleeve-type connecting member and a multiple piston chamber arrangement.

FIG. 7 is a cross-sectional view of the drill comprising a multiple piston arrangement and an internal rod-shaped connecting member.

Referring now to the preferred configuration of our invention shown in FIG. 1, it will be seen that the rock drill comprises in combination the stem adapter 10, which is the lower part of the drill stem (not shown) conventionally used in rock drilling; the vibrator or upper reciprocating massive member 20; the head or lower reciprocating massive member 40; the bit 50; and the sleeve 12.

The vibrator 20 is attached resiliently in the axial direction to the stem adapter 10 by means of the interposed elastomeric bearings or bushings 11. A telescoping arrangement with annular bearings is preferred as shown.

A long metal sleeve 12 connects the vibrator and head 40 through their threaded affixation locations 51. While the sleeve 12 provides the axial strength of the connection between the head and vibrator masses and carries the stresses generated by the operation of the drill, the plain rubber or rubber-metal laminated bearings, or any type of sliding bushvibratory tensile stresses for very long periods of time without succumbing to fatigue.

Construction of an improved vibratory drill apparatus possessing the aforesaid feature of an elongate stiffly resilient connecting means accordingly becomes the principle object of this invention, with other objects becoming more apparent upon reading of the following specification, considered and interpreted in the light of the accompanying drawings.

Of the drawings, details of which have been exaggerated to show the principle of the invention with the maximum degree of clarity;

FIG. 1 is an axial sectional view of the preferred configuration of the rock drill equipped with a tricone bit, and showing the metal sleeve connecting member in its relationship to the drill stern, vibrator and head assembly as well as the fluidic oscillator feeding a single piston chamber.

FIG. 2 is an axial sectional view of the piston chamber incorporating the mechanical oscillator.

FIG. 3 is an elevated view illustrating a bidirectionally slotted connecting member.

F IG. 4 is an elevated view of the connecting member unidirectionally slotted.

FIG. 5 is an elevated view of the drill illustrating a mechanical interconnection between the sleeve connecting member and the stem adapter.

ing, 16, serve to provide lateral support means and to secure the centering and alignment between sleeve, vibrator and head, and by their location in the annulus between sleeve and massive members to provide sealing against the pressurized fluid that powers the drill. This fluid, normally being forced downhole for the purpose of clearing the hole of rock debris, may be natural gas, air, water, oil or drilling mud as is the common practice in rock drilling. The fluid enters the drill as an inlet flow through the inlet opening 21 and is eventually carried to the bit 50 through the conduits 6a, 6b traversing the vibrator 20 and head 40.

It will be appreciated that the length and cross-sectional area of the sleeve 12 are such as to cause the sleeve to behave as a stifi spring connecting the members 20 and 40. Thus, the sleeve, vibrator, and head-bit constitute a spring-mass resonant dynamic system capable of being subjected to sustained vibratory motion in the axial direction, with the natural frequency of oscillation established by the magnitudes of the masses involved, the equivalent resilience constant of the spring, and the characteristics of the rock against which the drill is operating.

The laminated bearings 16, on the other hand, consist of a stack of thin metal laminates interleaved and adhered together by thin alternating layers of elastic rubber or other rubberlike material, the layering being in the form of concentric cylinders coaxial with the main axis of the drill. Such a layer of rubberlike material bonded between metal laminae can withstand high compressive loads applied by the metal layers, it being sufficiently thin as to be restrained from substantially flowing sidewise by its adhesion to the metal. Elastomeric bearings of this type, however, are capable of a deformation in shear parallel to the laminae, and behave in a soft springlike fashion little afiected by any compressive forces that may be applied perpendicularly to the layers.

A single piston chamber 34 is formed between the lower face 20a of the vibrator 20 and the upper face 40a of the head 40, said piston chamber, in combination with a subsequently described fluidic or mechanical oscillator, forming a fluid operated actuator that imparts oscillatory forces to the two massive members. The space enclosed by the piston chamber 34 is cyclically filled by the aforementioned pressurized fluid: as a result, during the half of a cycle when the flow is switched on the fluid pressure pushes the vibrator upward and the head downward, both motions taking place against the spring resistance of the sleeve 12. During the second half of the cycle when the flow is switched off the restoring force of the stretched sleeve forces the vibrator downward and the head upward. The cyclic switching or porting of the pressurized fluid into the piston chamber 34 and out of it is accomplished in a self-sustaining manner by means of either a fluidic oscillator 23 shown in FIG. 1, or by means of a mechanical oscillator shown in FIG. 2. Both oscillator types are called collectively the actuator.

The function of the fluidic oscillator is based on the principle of momentum exchange between fluid jets. Specifically, the pressurized fluid flowing in the conduit 6a is channeled into the source chamber 24 from where in a jet form 28 it proceeds into the interaction chamber 26; from the latter it starts streaming into the output duct, say 27a, to be discharged into the chamber 34. During this streaming through the duct 27a part of the fluid is diverted into the feedback tube 30a and reaches the feedback port 29a after some delay. This diverted flow entering the interaction chamber 26 impinges perpendicularly onto the main jet 28 causing it to be diverted or switched over to the output duct 27b. The trigonometric tangent of the flow 28, as diverted to effect the switching, is substantially equal to the ratio of the momentum of the feedback jet to the momentum of the main jet. This feedback action is repeated through the feedback tube 30b when the main flow enters the output duct 27b now causing the switching of the main jet 28 back into the output duct 27a where the cycle is reinitiated. The length of the cycle is established mainly by the length and the hydrodynamic impedance of the feedback tubes 30a and 30b. The shape of the interaction chamber 26 in this type of fluidic oscillator is such as to prevent wall attachment of the main jet on the sides of this chamber; this prevention is effected through the recess 26a, 26b. The output 27b of the oscillator, extending as a duct segment 29 into the upper part of the head 40, empties into the conduit 6b and eventually though central hole 52 or such jets or courses as may be provided in the bit, onto the bottom of the rock hole.

The gap 36 between the outer surface of the duct segment 29 and the inner surface of the conduit 6b, shown exaggerated in FIG. 1, is given an appropriate width facilitatingthe venting of the output of the oscillator 23 during the half cycle when the piston chamber 34 is active. Such venting may be important in making the operation of the oscillator independent of the load imposed by the particular rock drilled at the time. The shape of the gap 36 is shown as a cylindrical annulus is FIG. 1, but it may be of any other shape facilitating the emptying of the piston chamber 34 during the inactive half of the oscillation cycle. If the gap 36 has the shape of an upright cone then, as the volume of the piston chamber is squeezed during the inactive part of the cycle, the conical shape causes the gap to become wider allowing the outpouring of the spent fluid from the piston chamber into the conduit 6b. If, on the other hand, the gap 36 has the shape of an inverted cone, then during the above half cycle the spent fluid is to a great extent prevented from flowing through the narrowed gap and, instead, is forced up into the interaction chamber 26 through the duct 27a to join the jet 28 as it exits through the duct 27b. in place of the duct segment 29 any other connecting and sealing means may be used such as bellows.

FIG. 2 shows the fluidic oscillator 23 replaced by the pipeshaped mechanical oscillator 60 carried within the conduits 6a and 6 b by the elastomeric bearings a, 15b. While bearing 15!: is soft and serves only as centering means, the elastomeric bearings 15a have relatively soft spring characteristics. .let nozzles 61 through the lateral wall of the oscillator face the passage pairs 37a, 37b over a small clearance gap, the oscillator itself being always filled by the pressurized fluid. The function of the oscillator is greatly elaborated in he copending application. Depending on the relative axial position of the vibrator and oscillator 60, and because the inner openings of the passage pairs 37a, 37b are offset axially with respect to one another, pressurized fluid from the jet nozzles 61 is forced into either the piston chamber 34 or the lower conduit 61: alternatively, forcing the head 40 and vibrator 20 to reciprocate in opposite directions. A restricted outlet passage 65b provides pressures equalization between the interior of the oscillator 60 and the conduit 6b, and also maintains fluid circulation thus preventing the forming of deposits within the oscillator. A damper or dashpot is provided between the oscillator 60 and the vibrator 20 in the form of the piston chamber 75a, 75b on either side of the piston 75 communicating via the appropriately sized gap 63 between the piston 75 and the wall of the conduit 6a. The damper in effect couples the oscillator 60 to the vibrator 20 to create the proper phase of relative motion of the oscillator with respect to the head 40 and the vibrator 20. It is desirable that the mass of the mechanical oscillator 60 be made relatively small so that its position is determined primarily by the coaction of the damper and of the spring effect of the elastomeric bearing 15a as explained in great detail in the copending application.

Regarding now the connecting member 12, it is suggested that it be a long metal shell or sleeve of a substantially cylindrical shape, whose cross-sectional area transverse to the longitudinal axis is substantially constant and minimal, meaning that, despite occasional enlargements of cross-sectional area at the points of connection to the two massive members or at the massive alignment points midway between the connection points, the area over most of the sleeve's length is roughly constant and smaller than at the foresaid points, so that this minimal area experiences the maximum stress and strain and provides the bulk of the spring action. The active length of the sleeve, or stiffly elastic member, is defined to be the length of it between its connection points to each of the two massive members. The active length is thus subjected to the alternating compressional and tensile stress as axial oscillation takes place between the two massive members. By contrast to this active length the physical length of the sleeve may extend beyond the connection point to a massive member, one case of such extension being shown in FIG. 5 for the purpose of coupling the system to the stem adapter 10. Furthermore, although the connecting member 12 is described as being made of metal, the term metal" is qualified to mean any strong stiffly elastic material such as a fiber-reinforced or wire or strand-wound synthetic substance or the like. it is important that the transverse cross-sectional area of the connecting member is substantially minimal by comparison to the transverse cross-sectional area of the massive members, or that the connecting member has a lower modulus of elasticity than the massive members. Thus the connecting member will undergo substantially most of the compressional or elongational stretch when the system is subjected to oscillating axial forces.

In reference to the geometric shape of the connecting member it may be either that of a solid cylinder as depicted so far, or of a multiply slotted cylinder as shown in FIGS. 3 and 4. The slots are arranged in bands or arrays of helical arcs 9a of opposing handedness as in FIG. 3; the term handedness" referring to the direction of a helix as it advances along its axis (as in a right-handed screw for instance), This slotting of the cylinder wall in effect creates a plurality of elongate helical metal members or springs represented by the strong metal ribs 9b, which are preferably in a side-by-side array, and which, in combination with the sleeve lengths lefi unslotted, define the effective spring constant of the connecting member. The ribs can be viewed by themselves as elongate metal members carrying force between the two massive members and affixed at their ends to the remaining part of the sleeve. If, as shown in FIG, 4, the slots in all or most bands or arrays are sloped in the same direction with respect to the generatrix 12a of the cylinder, then they result in a combination of both linear and torsional springlike behavior of the connecting member similar to the behavior of the elastomeric bearing 12!: shown in FIG. 13 of the copending application. This dual characteristic may be exploited for automatically indexing the bit after every stroke as explained in the copending application. It will be appreciated that, instead of the bands of slots, a plurality of apertures of any shape through the sleeve s walls arranged into any appropriate pattern may be used.

While FIG. 1 of the present application shows the sleevetype connecting member 12 in its working arrangement with a single piston chamber 34, FlG. 6 shows the case where, because of power requirements, a plurality of piston chambers 34 is necessary between the head 40 and vibrator 20. ln this latter case the piston chambers are formed between flanges 35 formed on the outer cylindrical surface of the vibrator and flanges 41 formed on an inner shell 40a of the head as explained at length in the copending application. Internal passages for pressurized fluid supply and drain are supplied within the vibrator and head as shown in the copending application, and a fluidic oscillator or a mechanical oscillator (not shown) may be used as porting means.

FIG. 7 shows the connecting member 12 in the form of a rod, instead of a sleeve, with its threaded ends 51 rigidly affixed to the vibrator and head 40. The rod, whose primary dynamic function is to act as a stiff axial spring between the two massive members, runs through the conduits 6a and 6b. Centering and lateral support of the rod 12 is secured by the bearings 16 and 16a, of which 16 occupies fully the associated annulus acting as a seal, while the segments bearings 16a only partially occupy the associated annulus allowing the flow of pressurized fluid through them.

The set of longitudinal holes 52 arranged about the main axis at the ends of vibrator 20 and head 40 provide the appropriate passages for the flow of pressurized fluid. The bearings 17 on the other hand between the two massive members serve primarily as seals. Oscillator means, explained in detail in the copending application are not shown in FIG. 7 for the sake of clarity. However, it will be understood that the type of fluidic oscillator as depicted in FIG. 3 of the referenced specification could be employed, either singly or multiply in parallel, being contained within the body of vibrator 20 such that its inlet opening, corresponding to the referenced part 21 communicates with the internal passage 60 and its output opening or openings at the bottom of vibrator 20 corresponding to referenced part 22, discharges flow into the internal passage 6b. Altemately a form of mechanical oscillator whose design does not interfere with the connecting rod 12 may be used in this arrangement. The active length and minimal cross section of the connecting means in the form of the rod 12 are defined as those of the sleeve in the previous arrangement. instead of a single connecting rod along the apparatus longitudinal axis between the two massive members, there may obviously be provided two or more rods off center, each connecting the two massive together.

We have discussed in the original application, and above by using elongate spring members cut into a sleeve, means of obtaining an associated component of torsional motion along with the vibratory axial motion for purposes of self-indexing in rotation. Yet another means of doing this can be provided in the present case of a central rod connecting the two telescoped massive members. It is related to that in the copending application where in FIG. 13 one set of supporting laminate bearings are arranged in the annular space between opposing complementarily contoured faces of the inner and outer massive members that are not only sloped to create an axial spring effect but also are arranged in helical tracks. Thus a torsional component of motion accompanies the axial motion. In the present case the sloping of the support bearings 17 for axial spring effect is not used, but the helical tracks on opposing faces can be provided to obtain a torsional component. All or a part of the support bearings 17 in FIG. 7 can be so arranged.

While full and complete disclosure of the invention has been set forth in accordance with the dictates of the patent statutes, it is to be understood that the invention is not intended to be so limited. It will be apparent to those skilled in he art that various changes may be made to the embodiments described herein without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

l. A vibratory drill assembly as described including two massive members arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said two massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement of the one massive member with respect to the other results upon the application of axial force between said massive members, said connecting means having a cross section transverse to said axis that is different from the cross sections of either of said two massive members,

a bit drivingly attached to one of said massive members,

a fluid operated actuator producing oscillating force between said two massive members, including at least one efiective piston chamber to accept pressurized flow cyclically through porting means from oscillatory converting means acting upon an inlet flow of pressurized fluid and converting said inlet flow to said cyclic flow, whereby fluid energy may be converted to vibratory energy having about the frequency of the resonant oscillatory system formed by said massive members and said springlike behaving connecting means,

wherein said stiff springlike connecting means is an elongate metal member arranged along said longitudinal axis and having a cross-sectional area transverse to said longitudinal axis that is substantially constant and substantially minimal over a large portion of the length of said metal member to define an active length, said elongate metal member being affixed at one end of said active length to one of said massive members.

2. A vibratory drill assembly as described including two massive members arranged in opposing oscillatory relation to one another along a common longitudinal axis,

connecting means engaged with each of said two massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement of the one massive member with respect to the other results upon the application of axial force between said massive members, said connecting means having a cross section transverse to said axis that is different from the cross sections of either of said two massive members,

a bit drivingly attached to one of said massive members,

a fluid operated actuator producing oscillating forece between said two massive members, including at least one effective piston chamber to accept pressurized flow cyclically through porting means from oscillatory converting means acting upon an inlet flow of pressurized fluid and converting said inlet flow to said cyclic flow, whereby fluid energy may be converted to vibratory energy having about the frequency of the resonant oscillatory system formed by said massive members and said springlike behaving connecting means,

wherein said stiff springlike connecting means includes at least one elongate metal member that carries force between said two massive members and is affixed to each of the same at locations that are respectively spaced along the elongate dimension of said connecting elongate metal member.

3. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis,

connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members,

a bit drivingly attached to one of said massive members,

an actuator producing and applying an axial oscillatory force upon said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system,

and wherein said stiff springlike connecting means includes at least one elongate member that is affixed to each of said two massive members at locations that are respectively spaced along the elongate dimension of said connecting elongate metal member. and the total cross-sectional area of said connecting means transverse to said longitudinal axis is substantially less than the likewise transverse cross-sectional area of said massive members over a large portion of the distance between said spaced affixation locations.

4. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis,

connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members,

a bit drivingly attached to one of said massive members,

an actuator producing and applying an axial oscillatory force upon at least one of said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system,

and wherein said stiff springlike connecting means includes a plurality of elongate helical metal members that carry force between said two massive members and are affixed at locations that are respectively spaced along the elongate dimension of said helical metal members.

5. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis,

connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members,

a bit drivingly attached to one of said massive members,

an actuator producing and applying an axial oscillatory force upon at least one of said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system,

and wherein said springlike connecting means includes at least one elongate metal member that is affixed to each of said two massive members at locations that are respectively spaced along the elongate dimension of said connecting metal member, and said elongate metal member is made of a material having a lower modulus of elasticity than said massive members.

6. The device of claim 1 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part oftheir lengths.

7 The device of claim 1 wherein said elongate metal member is within and laterally supported by said massive members.

8. The device of claim 1 wherein said elongate meta] member has a tubular cross section and surrounds said massive members over at least part of their length and, in addition, provides lateral support to said massive members at a location spaced between the affixation locations at the ends of said active length.

9. The device of claim 8 wherein said lateral support means is provided by laminated rubber-metal bearings as described.

10. The device of claim 8 wherein each massive member IS laterally supported by a laminated rubber-metal bearing that fills the annulus between said massive member and the inside surface of said tubular member. and provides a seal against fluid passage between them.

11. The device of claim 2 wherein said elongate metal members are helical and are plural in number arranged in at least one side-by-side array about said longitudinal axis, as could be defined by cutting spaced helical slots through the wall of a tubular member.

12. The device of claim 11 wherein a plurality of said sideby-side arrays are provided spaced along said longitudinal axis, and the handedness of said helical elongate metal members are such that a substantial torsional component of motion about said longitudinal axis accompanies said limited axial displacement upon the application of axial force.

13. The device of claim 2 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their lengths.

14. The device of claim 2 wherein said elongate metal members are a plurality of rods within and laterally supported by said massive members.

15. The device of claim 2 wherein said oscillatory converting means includes at least one fluidic oscillator contained within one of said massive members and ducted to said piston chamber, said fluidic oscillator having a source chamber fed by said inlet flow, and interaction chamber communicating with said source chamber, a pair of output ducts connected to said interaction chamber, the downstream end of one of said output ducts connected to said piston chamber and the downstream end of the second of said output ducts connected to a conduit traversing the second said massive member, and feedback paths connecting said interaction chamber to points downstream of said output ducts.

16. The device of claim 15 wherein said second output duct is connected to said conduit traversing said second massive member by means ofa duct segment, said duct segment forming a gap between itself and said conduit, said gap having the shape ofa cone.

17. The device of claim 2 wherein said oscillatory converting means includes a mechanical oscillator having at least one nozzle that forms a fluid jet from said inlet flow of pressurized fluid. said mechanical oscillator on the one hand being supported relatively to one of said massive members by axial spring-behaving support means allowing reciprocating movement and on the other hand being affected by the movement of the second massive member through a damper provided between said second massive member and said mechanical oscillator, said mechanical oscillator reciprocating through a distance whereby said jets are caused to impinge cyclically upon passage pairs communicating with said piston chamber and with a conduit traversing one said massive member.

18. The device of claim 3 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their length and in addition provides lateral support to said massive members at a location spaced between the afftxation locations at the ends of the active length of said elongate metal member.

19. The device of claim 18 wherein each massive member is laterally supported by a laminated rubber-metal bearing that fills the annulus between said massive member and the inside surface of said tubular member and provides a seal against fluid passage between them.

20. The device of claim 4 wherein the handedness of said plurality of elongate helical metal members is such that a substantial torsional component of motion about said longitudinal axis accompanies said limited axial displacement upon the application of axial force.

21. The device of claim 2 wherein said elongate metal member is a sleeve that carries a pattern of apertures through its walls.

22. The device of claim 2 wherein said elongate metal member is within and is laterally supported by said massive members, and one said massive member telescopes within the other and is aligned and attached thereto by bearing means.

23. The device of claim 22 wherein the means of said lateral support and said bearing means include at least one laminated rubber-metal bearing.

24. The device of claim 22 wherein said bearing means includes complementally contoured helical tracks in said two massive members whereby a torsional component of motion accompanies said axial oscillatory motion. 

1. A vibratory drill assembly as described including two massive members arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said two massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement of the one massive member with respect to the other results upon the application of axial force between said massive members, said connecting means having a cross section transverse to said axis that is different from the cross sections of either of said two massive members, a bit drivingly attached to one of said massive members, a fluid operated actuator producing oscillating force between said two massive members, including at least one effective piston chamber to accept pressurized flow cyclically through porting means from oscillatory converting means acting upon an inlet flow of pressurized fluid and converting said inlet flow to said cyclic flow, whereby fluid energy may be converted to vibratory energy having about the frequency of the resonant oscillatory system formed by said massive members and said springlike behaving connecting means, wherein said stiff springlike connecting means is an elongate metal member arranged along said longitudinal axis and having a cross-sectional area transverse to said longitudinal axis that is substantially constant and substantially minimal over a large portion of the length of said metal member to define an active length, said elongate metal member being affixed at one end of said active length to one of said massive members.
 2. A vibratory drill assembly as described including two massive members arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said two massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement of the one massive member with respect to the other results upon the application of axial force between said massive members, said connecting means having a cross section transverse to said axis that is different from the cross sections of either of said two massive members, a bit drivingly attached to one of said massive members, a fluid operated actuator producing oscillating forece between said two massive members, including at least one effective piston chamber to accept pressurized flow cyclically through porting means from oscillatory converting means acting upon an inlet flow of pressurized fluid and converting said inlet flow to said cyclic flow, whereby fluid energy may be converted to vibratory energy having about the frequency of the resonant oscillatory system formed by said massive members and said springlike behaving connecting means, wherein said stiff springlike connecting means includes at least one elongate metal member that carries force between said two massive members and is affixed to each of the same at locations that are respectively spaced along the elongate dimension of said connecting elongate metal member.
 3. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members, a bit drivingly attached to one of said massive members, an actuator producing and applying an axial oscillatory force upon said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system, and wherein said stiff springlike connecting means includes at least one elongate member that is affixed to each of said two massive members at locations that are respectively spaced along the elongate dimension of said connecting elongate metal member, and the total cross-sectional area of said connecting means transverse to said longitudinal axis is substantially less than the likewise transverse cross-sectional area of said massive members over a large portion of the distance between said spaced affixation locations.
 4. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members, a bit drivingly attached to one of said massive members, an actuator producing and applying an axial oscillatory force upon at least one of said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system, and wherein said stiff springlike connecting means includes a plurality of elongate helical metal members that carry force between said two massive members and are affixed at locations that are respectively spaced along the elongate dimension of said helicAl metal members.
 5. A vibratory drill assembly as described including two massive members being arranged in opposing oscillatory relation to one another along a common longitudinal axis, connecting means engaged with each of said massive members and attaching them together, said connective means having the properties of a stiff spring in the direction of said common axis, whereby limited axial displacement occurs between said two massive members upon the application of axial force between said massive members, a bit drivingly attached to one of said massive members, an actuator producing and applying an axial oscillatory force upon at least one of said two massive members at about the natural frequency of the resonant system formed by said massive members and said springlike behaving connecting means, whereby oscillatory energy is imparted to said resonant system, and wherein said springlike connecting means includes at least one elongate metal member that is affixed to each of said two massive members at locations that are respectively spaced along the elongate dimension of said connecting metal member, and said elongate metal member is made of a material having a lower modulus of elasticity than said massive members.
 6. The device of claim 1 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their lengths.
 7. The device of claim 1 wherein said elongate metal member is within and laterally supported by said massive members.
 8. The device of claim 1 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their length and, in addition, provides lateral support to said massive members at a location spaced between the affixation locations at the ends of said active length.
 9. The device of claim 8 wherein said lateral support means is provided by laminated rubber-metal bearings as described.
 10. The device of claim 8 wherein each massive member is laterally supported by a laminated rubber-metal bearing that fills the annulus between said massive member and the inside surface of said tubular member, and provides a seal against fluid passage between them.
 11. The device of claim 2 wherein said elongate metal members are helical and are plural in number arranged in at least one side-by-side array about said longitudinal axis, as could be defined by cutting spaced helical slots through the wall of a tubular member.
 12. The device of claim 11 wherein a plurality of said side-by-side arrays are provided spaced along said longitudinal axis, and the handedness of said helical elongate metal members are such that a substantial torsional component of motion about said longitudinal axis accompanies said limited axial displacement upon the application of axial force.
 13. The device of claim 2 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their lengths.
 14. The device of claim 2 wherein said elongate metal members are a plurality of rods within and laterally supported by said massive members.
 15. The device of claim 2 wherein said oscillatory converting means includes at least one fluidic oscillator contained within one of said massive members and ducted to said piston chamber, said fluidic oscillator having a source chamber fed by said inlet flow, and interaction chamber communicating with said source chamber, a pair of output ducts connected to said interaction chamber, the downstream end of one of said output ducts connected to said piston chamber and the downstream end of the second of said output ducts connected to a conduit traversing the second said massive member, and feedback paths connecting said interaction chamber to points downstream of said output ducts.
 16. The device of claim 15 wherein said second output duct is connected to said conduit traversing said second massive member by means of a duct segment, said duct segmEnt forming a gap between itself and said conduit, said gap having the shape of a cone.
 17. The device of claim 2 wherein said oscillatory converting means includes a mechanical oscillator having at least one nozzle that forms a fluid jet from said inlet flow of pressurized fluid, said mechanical oscillator on the one hand being supported relatively to one of said massive members by axial spring-behaving support means allowing reciprocating movement and on the other hand being affected by the movement of the second massive member through a damper provided between said second massive member and said mechanical oscillator, said mechanical oscillator reciprocating through a distance whereby said jets are caused to impinge cyclically upon passage pairs communicating with said piston chamber and with a conduit traversing one said massive member.
 18. The device of claim 3 wherein said elongate metal member has a tubular cross section and surrounds said massive members over at least part of their length and in addition provides lateral support to said massive members at a location spaced between the affixation locations at the ends of the active length of said elongate metal member.
 19. The device of claim 18 wherein each massive member is laterally supported by a laminated rubber-metal bearing that fills the annulus between said massive member and the inside surface of said tubular member and provides a seal against fluid passage between them.
 20. The device of claim 4 wherein the handedness of said plurality of elongate helical metal members is such that a substantial torsional component of motion about said longitudinal axis accompanies said limited axial displacement upon the application of axial force.
 21. The device of claim 2 wherein said elongate metal member is a sleeve that carries a pattern of apertures through its walls.
 22. The device of claim 2 wherein said elongate metal member is within and is laterally supported by said massive members, and one said massive member telescopes within the other and is aligned and attached thereto by bearing means.
 23. The device of claim 22 wherein the means of said lateral support and said bearing means include at least one laminated rubber-metal bearing.
 24. The device of claim 22 wherein said bearing means includes complementally contoured helical tracks in said two massive members whereby a torsional component of motion accompanies said axial oscillatory motion. 